The XAllocStandardColormap function allocates and returns
a pointer to a XStandardColormap structure. Note that all fields in the
XStandardColormap structure are initially set to zero. If insufficient
memory is available, XAllocStandardColormap returns NULL. To free the
memory allocated to this structure, use XFree.

The XSetRGBColormaps
function replaces the RGB colormap definition in the specified property
on the named window. If the property does not already exist, XSetRGBColormaps
sets the RGB colormap definition in the specified property on the named
window. The property is stored with a type of RGB_COLOR_MAP and a format
of 32. Note that it is the caller's responsibility to honor the ICCCM restriction
that only RGB_DEFAULT_MAP contain more than one definition.

The XSetRGBColormaps
function usually is only used by window or session managers. To create
a standard colormap, follow this procedure:

1.

Open a new connection to
the same server.

2.

Grab the server.

3.

See if the property is on the property
list of the root window for the screen.

4.

If the desired property is not
present:

·

Create a colormap (unless you are using the default colormap of
the screen).

The XGetRGBColormaps function returns the RGB colormap definitions
stored in the specified property on the named window. If the property exists,
is of type RGB_COLOR_MAP, is of format 32, and is long enough to contain
a colormap definition, XGetRGBColormaps allocates and fills in space
for the returned colormaps and returns a nonzero status. If the visualid
is not present, XGetRGBColormaps assumes the default visual for the
screen on which the window is located; if the killid is not present,
None is assumed, which indicates that the resources cannot be released.
Otherwise, none of the fields are set, and XGetRGBColormaps returns
a zero status. Note that it is the caller's responsibility to honor the ICCCM
restriction that only RGB_DEFAULT_MAP contain more than one definition.

The colormap member is the colormap created by the XCreateColormap function.
The red_max, green_max, and blue_max members give the maximum red, green,
and blue values, respectively. Each color coefficient ranges from zero
to its max, inclusive. For example, a common colormap allocation is 3/3/2
(3 planes for red, 3 planes for green, and 2 planes for blue). This colormap
would have red_max = 7, green_max = 7, and blue_max = 3. An alternate
allocation that uses only 216 colors is red_max = 5, green_max = 5, and
blue_max = 5.

The red_mult, green_mult, and blue_mult members give the scale
factors used to compose a full pixel value. (See the discussion of the
base_pixel members for further information.) For a 3/3/2 allocation, red_mult
might be 32, green_mult might be 4, and blue_mult might be 1. For a 6-colors-each
allocation, red_mult might be 36, green_mult might be 6, and blue_mult
might be 1.

The base_pixel member gives the base pixel value used to compose
a full pixel value. Usually, the base_pixel is obtained from a call to
the XAllocColorPlanes function. Given integer red, green, and blue
coefficients in their appropriate ranges, one then can compute a corresponding
pixel value by using the following expression:

Negative multipliers can be represented by converting the 2's complement
representation of the multiplier into an unsigned long and storing the
result in the appropriate _mult field. The step of masking by 0xFFFFFFFF
effectively converts the resulting positive multiplier into a negative
one. The masking step will take place automatically on many machine architectures,
depending on the size of the integer type used to do the computation,

The
visualid member gives the ID number of the visual from which the colormap
was created. The killid member gives a resource ID that indicates whether
the cells held by this standard colormap are to be released by freeing
the colormap ID or by calling the XKillClient function on the indicated
resource. (Note that this method is necessary for allocating out of an existing
colormap.)

The properties containing the XStandardColormap information
have the type RGB_COLOR_MAP.